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ASSIGNMENT QUESTION
YOUR COLLEGE IS HOSTING AN INTERNATIONAL EXPO ON TECHNICAL EDUCATION IN ZIMBABWEPREPARE A POWERPOINT PRESENTATION BASED ON UNDERPINNING OF FOUNDATIONSYOUR PRESENTATION SHOULD HAVE CLEAR amp INFORMATIVE ILLUSTRATIONS amp SHOULD FOLLOW THE FOLLOWING FORMAT
(a) DEFINITIONS
(b) REASONS FOR UNDERPINNING
(c) PROCEDURE USING THE
FOLLOWING MATERIALS
i CONCRETE
ii BEAMS
iii MINI PILES
UNDERPINNING
CHAKAMBA J
UNDERPINNING
OBJECTIVES
bull Define the term underpinning
bull Describe underpinningwhen it is needed and how it is done
bull State the reasons for underpinning
bull State the methods of underpinning a structure
UNDERPINNING OF BUILDINGS
INTRODUCTIONWhenever a new building is to be built especially
in urban areasit is quite common to have the foundations lower than the foundations of adjacent buildings
It is therefore essential that the stability of the existing building(s) is safeguarded by performing underpinning as well as shoring`that care and forethought should be undertaken if these operations are to be successfully carried out
Only highly skillied and experienced personnel or companies should perform these operations
DEFINITIONSTECHNICAL EDUCATIONbull It is academic and vocational preparation of students for jobs
involving applied science and modern technology bull It is also understood to include the theoretical amp practical scientific
knowledge and skills that permit a person receiving such education to solve production engineering and economic problems in his speciality(encyclopedia2 the freedictionary)
UNDERPINNINGbull It is a broad term to describe the process of modifying
an existing foundation by adding supportbull It can also be described as the installation of temporary
or permanent support to an existing foundation to provide either additional depth or an increase in bearing capacity(Nemati 2007)
DEFINITIONS Cont
bull Underpinning can also be reffered to as a process of strengthening the foundation of an existing building or other structure(wikipediathe free encyclopedia)
REASONS FOR UNDERPINNING Construction of a new project with a deeper
foundation adjacent to an existing building
To enable the foundations to be deepened for structural reasons eg to construct a basement or addition of another storey to the building
REASONS contTo support a structure that is sinking or tilting due to
poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a
structure when excavating close to or below its foundation level
To support a structure while making alteration to its foundations or main supporting members
To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels
To enable a building to be moved bodily to a new site
REASONS ContThe original foundation is simply not strong or
stable enough
The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages
Settlement of an existing structure
UNDERPINNED FOUNDATIONS
SOME CAUSES OF SETTLEMENT ON A BUILDING
Lowering of the water table due to tidal fluctuationswellsfor a water district etc
Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning
Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning
Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement
Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings
DETERMINING THE NEED FOR UNDERPINNING
Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations
When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis
Data collected or readings will indicate if the movements are decreasing or increasing
Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses
Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146
PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING
The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures
that they are all in line
THE PROCESS
A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make
penetration into the ground easier is placed into position below the foundation
A bearing plate is then positioned between the jack and the foundation
PROCESS contThe jack is then put between the first section and the
bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation
When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections
As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections
The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
UNDERPINNING
CHAKAMBA J
UNDERPINNING
OBJECTIVES
bull Define the term underpinning
bull Describe underpinningwhen it is needed and how it is done
bull State the reasons for underpinning
bull State the methods of underpinning a structure
UNDERPINNING OF BUILDINGS
INTRODUCTIONWhenever a new building is to be built especially
in urban areasit is quite common to have the foundations lower than the foundations of adjacent buildings
It is therefore essential that the stability of the existing building(s) is safeguarded by performing underpinning as well as shoring`that care and forethought should be undertaken if these operations are to be successfully carried out
Only highly skillied and experienced personnel or companies should perform these operations
DEFINITIONSTECHNICAL EDUCATIONbull It is academic and vocational preparation of students for jobs
involving applied science and modern technology bull It is also understood to include the theoretical amp practical scientific
knowledge and skills that permit a person receiving such education to solve production engineering and economic problems in his speciality(encyclopedia2 the freedictionary)
UNDERPINNINGbull It is a broad term to describe the process of modifying
an existing foundation by adding supportbull It can also be described as the installation of temporary
or permanent support to an existing foundation to provide either additional depth or an increase in bearing capacity(Nemati 2007)
DEFINITIONS Cont
bull Underpinning can also be reffered to as a process of strengthening the foundation of an existing building or other structure(wikipediathe free encyclopedia)
REASONS FOR UNDERPINNING Construction of a new project with a deeper
foundation adjacent to an existing building
To enable the foundations to be deepened for structural reasons eg to construct a basement or addition of another storey to the building
REASONS contTo support a structure that is sinking or tilting due to
poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a
structure when excavating close to or below its foundation level
To support a structure while making alteration to its foundations or main supporting members
To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels
To enable a building to be moved bodily to a new site
REASONS ContThe original foundation is simply not strong or
stable enough
The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages
Settlement of an existing structure
UNDERPINNED FOUNDATIONS
SOME CAUSES OF SETTLEMENT ON A BUILDING
Lowering of the water table due to tidal fluctuationswellsfor a water district etc
Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning
Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning
Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement
Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings
DETERMINING THE NEED FOR UNDERPINNING
Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations
When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis
Data collected or readings will indicate if the movements are decreasing or increasing
Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses
Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146
PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING
The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures
that they are all in line
THE PROCESS
A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make
penetration into the ground easier is placed into position below the foundation
A bearing plate is then positioned between the jack and the foundation
PROCESS contThe jack is then put between the first section and the
bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation
When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections
As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections
The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
UNDERPINNING
OBJECTIVES
bull Define the term underpinning
bull Describe underpinningwhen it is needed and how it is done
bull State the reasons for underpinning
bull State the methods of underpinning a structure
UNDERPINNING OF BUILDINGS
INTRODUCTIONWhenever a new building is to be built especially
in urban areasit is quite common to have the foundations lower than the foundations of adjacent buildings
It is therefore essential that the stability of the existing building(s) is safeguarded by performing underpinning as well as shoring`that care and forethought should be undertaken if these operations are to be successfully carried out
Only highly skillied and experienced personnel or companies should perform these operations
DEFINITIONSTECHNICAL EDUCATIONbull It is academic and vocational preparation of students for jobs
involving applied science and modern technology bull It is also understood to include the theoretical amp practical scientific
knowledge and skills that permit a person receiving such education to solve production engineering and economic problems in his speciality(encyclopedia2 the freedictionary)
UNDERPINNINGbull It is a broad term to describe the process of modifying
an existing foundation by adding supportbull It can also be described as the installation of temporary
or permanent support to an existing foundation to provide either additional depth or an increase in bearing capacity(Nemati 2007)
DEFINITIONS Cont
bull Underpinning can also be reffered to as a process of strengthening the foundation of an existing building or other structure(wikipediathe free encyclopedia)
REASONS FOR UNDERPINNING Construction of a new project with a deeper
foundation adjacent to an existing building
To enable the foundations to be deepened for structural reasons eg to construct a basement or addition of another storey to the building
REASONS contTo support a structure that is sinking or tilting due to
poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a
structure when excavating close to or below its foundation level
To support a structure while making alteration to its foundations or main supporting members
To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels
To enable a building to be moved bodily to a new site
REASONS ContThe original foundation is simply not strong or
stable enough
The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages
Settlement of an existing structure
UNDERPINNED FOUNDATIONS
SOME CAUSES OF SETTLEMENT ON A BUILDING
Lowering of the water table due to tidal fluctuationswellsfor a water district etc
Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning
Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning
Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement
Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings
DETERMINING THE NEED FOR UNDERPINNING
Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations
When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis
Data collected or readings will indicate if the movements are decreasing or increasing
Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses
Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146
PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING
The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures
that they are all in line
THE PROCESS
A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make
penetration into the ground easier is placed into position below the foundation
A bearing plate is then positioned between the jack and the foundation
PROCESS contThe jack is then put between the first section and the
bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation
When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections
As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections
The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
UNDERPINNING OF BUILDINGS
INTRODUCTIONWhenever a new building is to be built especially
in urban areasit is quite common to have the foundations lower than the foundations of adjacent buildings
It is therefore essential that the stability of the existing building(s) is safeguarded by performing underpinning as well as shoring`that care and forethought should be undertaken if these operations are to be successfully carried out
Only highly skillied and experienced personnel or companies should perform these operations
DEFINITIONSTECHNICAL EDUCATIONbull It is academic and vocational preparation of students for jobs
involving applied science and modern technology bull It is also understood to include the theoretical amp practical scientific
knowledge and skills that permit a person receiving such education to solve production engineering and economic problems in his speciality(encyclopedia2 the freedictionary)
UNDERPINNINGbull It is a broad term to describe the process of modifying
an existing foundation by adding supportbull It can also be described as the installation of temporary
or permanent support to an existing foundation to provide either additional depth or an increase in bearing capacity(Nemati 2007)
DEFINITIONS Cont
bull Underpinning can also be reffered to as a process of strengthening the foundation of an existing building or other structure(wikipediathe free encyclopedia)
REASONS FOR UNDERPINNING Construction of a new project with a deeper
foundation adjacent to an existing building
To enable the foundations to be deepened for structural reasons eg to construct a basement or addition of another storey to the building
REASONS contTo support a structure that is sinking or tilting due to
poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a
structure when excavating close to or below its foundation level
To support a structure while making alteration to its foundations or main supporting members
To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels
To enable a building to be moved bodily to a new site
REASONS ContThe original foundation is simply not strong or
stable enough
The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages
Settlement of an existing structure
UNDERPINNED FOUNDATIONS
SOME CAUSES OF SETTLEMENT ON A BUILDING
Lowering of the water table due to tidal fluctuationswellsfor a water district etc
Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning
Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning
Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement
Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings
DETERMINING THE NEED FOR UNDERPINNING
Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations
When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis
Data collected or readings will indicate if the movements are decreasing or increasing
Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses
Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146
PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING
The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures
that they are all in line
THE PROCESS
A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make
penetration into the ground easier is placed into position below the foundation
A bearing plate is then positioned between the jack and the foundation
PROCESS contThe jack is then put between the first section and the
bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation
When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections
As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections
The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
INTRODUCTIONWhenever a new building is to be built especially
in urban areasit is quite common to have the foundations lower than the foundations of adjacent buildings
It is therefore essential that the stability of the existing building(s) is safeguarded by performing underpinning as well as shoring`that care and forethought should be undertaken if these operations are to be successfully carried out
Only highly skillied and experienced personnel or companies should perform these operations
DEFINITIONSTECHNICAL EDUCATIONbull It is academic and vocational preparation of students for jobs
involving applied science and modern technology bull It is also understood to include the theoretical amp practical scientific
knowledge and skills that permit a person receiving such education to solve production engineering and economic problems in his speciality(encyclopedia2 the freedictionary)
UNDERPINNINGbull It is a broad term to describe the process of modifying
an existing foundation by adding supportbull It can also be described as the installation of temporary
or permanent support to an existing foundation to provide either additional depth or an increase in bearing capacity(Nemati 2007)
DEFINITIONS Cont
bull Underpinning can also be reffered to as a process of strengthening the foundation of an existing building or other structure(wikipediathe free encyclopedia)
REASONS FOR UNDERPINNING Construction of a new project with a deeper
foundation adjacent to an existing building
To enable the foundations to be deepened for structural reasons eg to construct a basement or addition of another storey to the building
REASONS contTo support a structure that is sinking or tilting due to
poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a
structure when excavating close to or below its foundation level
To support a structure while making alteration to its foundations or main supporting members
To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels
To enable a building to be moved bodily to a new site
REASONS ContThe original foundation is simply not strong or
stable enough
The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages
Settlement of an existing structure
UNDERPINNED FOUNDATIONS
SOME CAUSES OF SETTLEMENT ON A BUILDING
Lowering of the water table due to tidal fluctuationswellsfor a water district etc
Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning
Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning
Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement
Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings
DETERMINING THE NEED FOR UNDERPINNING
Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations
When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis
Data collected or readings will indicate if the movements are decreasing or increasing
Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses
Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146
PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING
The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures
that they are all in line
THE PROCESS
A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make
penetration into the ground easier is placed into position below the foundation
A bearing plate is then positioned between the jack and the foundation
PROCESS contThe jack is then put between the first section and the
bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation
When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections
As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections
The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
DEFINITIONSTECHNICAL EDUCATIONbull It is academic and vocational preparation of students for jobs
involving applied science and modern technology bull It is also understood to include the theoretical amp practical scientific
knowledge and skills that permit a person receiving such education to solve production engineering and economic problems in his speciality(encyclopedia2 the freedictionary)
UNDERPINNINGbull It is a broad term to describe the process of modifying
an existing foundation by adding supportbull It can also be described as the installation of temporary
or permanent support to an existing foundation to provide either additional depth or an increase in bearing capacity(Nemati 2007)
DEFINITIONS Cont
bull Underpinning can also be reffered to as a process of strengthening the foundation of an existing building or other structure(wikipediathe free encyclopedia)
REASONS FOR UNDERPINNING Construction of a new project with a deeper
foundation adjacent to an existing building
To enable the foundations to be deepened for structural reasons eg to construct a basement or addition of another storey to the building
REASONS contTo support a structure that is sinking or tilting due to
poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a
structure when excavating close to or below its foundation level
To support a structure while making alteration to its foundations or main supporting members
To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels
To enable a building to be moved bodily to a new site
REASONS ContThe original foundation is simply not strong or
stable enough
The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages
Settlement of an existing structure
UNDERPINNED FOUNDATIONS
SOME CAUSES OF SETTLEMENT ON A BUILDING
Lowering of the water table due to tidal fluctuationswellsfor a water district etc
Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning
Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning
Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement
Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings
DETERMINING THE NEED FOR UNDERPINNING
Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations
When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis
Data collected or readings will indicate if the movements are decreasing or increasing
Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses
Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146
PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING
The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures
that they are all in line
THE PROCESS
A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make
penetration into the ground easier is placed into position below the foundation
A bearing plate is then positioned between the jack and the foundation
PROCESS contThe jack is then put between the first section and the
bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation
When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections
As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections
The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
DEFINITIONS Cont
bull Underpinning can also be reffered to as a process of strengthening the foundation of an existing building or other structure(wikipediathe free encyclopedia)
REASONS FOR UNDERPINNING Construction of a new project with a deeper
foundation adjacent to an existing building
To enable the foundations to be deepened for structural reasons eg to construct a basement or addition of another storey to the building
REASONS contTo support a structure that is sinking or tilting due to
poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a
structure when excavating close to or below its foundation level
To support a structure while making alteration to its foundations or main supporting members
To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels
To enable a building to be moved bodily to a new site
REASONS ContThe original foundation is simply not strong or
stable enough
The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages
Settlement of an existing structure
UNDERPINNED FOUNDATIONS
SOME CAUSES OF SETTLEMENT ON A BUILDING
Lowering of the water table due to tidal fluctuationswellsfor a water district etc
Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning
Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning
Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement
Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings
DETERMINING THE NEED FOR UNDERPINNING
Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations
When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis
Data collected or readings will indicate if the movements are decreasing or increasing
Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses
Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146
PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING
The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures
that they are all in line
THE PROCESS
A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make
penetration into the ground easier is placed into position below the foundation
A bearing plate is then positioned between the jack and the foundation
PROCESS contThe jack is then put between the first section and the
bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation
When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections
As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections
The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
REASONS contTo support a structure that is sinking or tilting due to
poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a
structure when excavating close to or below its foundation level
To support a structure while making alteration to its foundations or main supporting members
To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels
To enable a building to be moved bodily to a new site
REASONS ContThe original foundation is simply not strong or
stable enough
The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages
Settlement of an existing structure
UNDERPINNED FOUNDATIONS
SOME CAUSES OF SETTLEMENT ON A BUILDING
Lowering of the water table due to tidal fluctuationswellsfor a water district etc
Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning
Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning
Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement
Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings
DETERMINING THE NEED FOR UNDERPINNING
Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations
When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis
Data collected or readings will indicate if the movements are decreasing or increasing
Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses
Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146
PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING
The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures
that they are all in line
THE PROCESS
A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make
penetration into the ground easier is placed into position below the foundation
A bearing plate is then positioned between the jack and the foundation
PROCESS contThe jack is then put between the first section and the
bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation
When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections
As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections
The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
REASONS ContThe original foundation is simply not strong or
stable enough
The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages
Settlement of an existing structure
UNDERPINNED FOUNDATIONS
SOME CAUSES OF SETTLEMENT ON A BUILDING
Lowering of the water table due to tidal fluctuationswellsfor a water district etc
Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning
Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning
Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement
Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings
DETERMINING THE NEED FOR UNDERPINNING
Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations
When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis
Data collected or readings will indicate if the movements are decreasing or increasing
Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses
Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146
PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING
The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures
that they are all in line
THE PROCESS
A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make
penetration into the ground easier is placed into position below the foundation
A bearing plate is then positioned between the jack and the foundation
PROCESS contThe jack is then put between the first section and the
bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation
When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections
As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections
The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
UNDERPINNED FOUNDATIONS
SOME CAUSES OF SETTLEMENT ON A BUILDING
Lowering of the water table due to tidal fluctuationswellsfor a water district etc
Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning
Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning
Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement
Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings
DETERMINING THE NEED FOR UNDERPINNING
Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations
When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis
Data collected or readings will indicate if the movements are decreasing or increasing
Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses
Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146
PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING
The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures
that they are all in line
THE PROCESS
A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make
penetration into the ground easier is placed into position below the foundation
A bearing plate is then positioned between the jack and the foundation
PROCESS contThe jack is then put between the first section and the
bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation
When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections
As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections
The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
SOME CAUSES OF SETTLEMENT ON A BUILDING
Lowering of the water table due to tidal fluctuationswellsfor a water district etc
Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning
Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning
Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement
Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings
DETERMINING THE NEED FOR UNDERPINNING
Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations
When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis
Data collected or readings will indicate if the movements are decreasing or increasing
Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses
Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146
PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING
The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures
that they are all in line
THE PROCESS
A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make
penetration into the ground easier is placed into position below the foundation
A bearing plate is then positioned between the jack and the foundation
PROCESS contThe jack is then put between the first section and the
bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation
When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections
As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections
The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
DETERMINING THE NEED FOR UNDERPINNING
Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations
When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis
Data collected or readings will indicate if the movements are decreasing or increasing
Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses
Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146
PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING
The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures
that they are all in line
THE PROCESS
A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make
penetration into the ground easier is placed into position below the foundation
A bearing plate is then positioned between the jack and the foundation
PROCESS contThe jack is then put between the first section and the
bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation
When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections
As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections
The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING
The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures
that they are all in line
THE PROCESS
A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make
penetration into the ground easier is placed into position below the foundation
A bearing plate is then positioned between the jack and the foundation
PROCESS contThe jack is then put between the first section and the
bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation
When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections
As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections
The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
PROCESS contThe jack is then put between the first section and the
bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation
When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections
As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections
The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont
The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted
The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them
A batten should now be fixed along the face of the wall throughout its length to act as a datum
A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
PROCEDURE contNo two adjacent bays must be excavated at the
same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay
Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug
The earth is then dug out from underneath the foundations until new level is reached
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
PROCEDURE contThe ground is now levelled and thoroughly rammed
The projection of the foundations is cut off so that it is flush with the face of the wall
The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first
The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14
The work should be thoroughly pinned up to the concrete
The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
UNDERPINNING OF FOUNDATIONS
UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
UNDERPINNING METHODSo The means and methods of supporting a
structure foundation depends on some of the following factors
Foundation Loads static and dynamicpermanent and temporary
Type and magnitude of allowable structural movement iedeformations
Subsurface soil conditions
Subsurface ground water conditions
Access and mobility to the foundations
Potential for environmental hazards
Seismic loading
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
WAYS OF ACHIEVING UNDERPINNING It can be done by
i Load transfer
ii Soil treatment or
iii A combination of the above two mechanisms
LOAD TRANSFER
This literally take structural loads and transfer them to an underlying stratum that is more suitable for support
SOIL TREATMENT
This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations
In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
UNDERPINNING METHODS There are numerous methods that can be used
when underpinning
Each methods having its own specific soil and loading conditions where its application is most effective
In some cases constructability can also determine the system to be used
Each method have also its own advantages and disadvantages depending on the specific characteristics of the project
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
1 CONVENTIONAL PIT METHOD
o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material
o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD
i It often results in moderate deformation of the structureii Unsafe working conditions
ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
2 JET GROUTING
It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system
It is an in-situ method of construction undertaken beneath foundations
High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2
Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING
SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and
sequenced so that little or no structural deformation occurs
ii It is most widely used for underpinning historical and sensitive structures
iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
3MICROPILES It is used to stabilize or upgrade existing foundation by
installing micropiles through pre-drilled holes determined by load characteristics
Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it
These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure
Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
ADVANTAGES OF MICROPILESi They have high carrying capacity
ii Less site constraint problems
iii Low noise and vibration
iv It is a self ndashsustained operation
v It can be designed to have very low settlement
DISADVANTAGES OF MICROPILES
i Higher cost as compared to other pilling systems
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
TYPES OF MICROPILES Pile and Beam
Pile and Cantilever Beam
Knuckle pile
Piled raft
Angle pile
Cantilever Ring Beam
Twin pile
Jack Down piles
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
METHODS OF UNDERPINNING
1NEEDLE BEAM 2NEEDLE WALL
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
UNDERPINNING METHODS
3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
UNDERPINNING METHODS
FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
CONCLUSIONbull Finally it is important to note that underpinning
works require experts in the design and execution levels
bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
REFERENCES
httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014
httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014
NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd
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